Telecommunication system



3 lSheets-Sheet l Filed Dec. 26, 1951 A INVENTOR. GEORGE ELL/O77' A TTORNE V Feb. 23, 1954 C,- E| |QTT 2,670,406

TELECOMMUNICATION SYSTEM Filed Dec. 26, 1951 3 Sheets-Sheet 2 0F Y 0N F/G. 4 (Xg y) X ON T0 COMMON ///ONl B TEST BUSY KEY BY if@ A TTOR/VE V Feb. 23, 1954 G, E| |QTT TELECOMMUNICATION SYSTEM 3 Sheets-Sheet 3 Filed Dec. 26, 1951 DGT TG. arm BG N IND. COM. W/R/NG IIT@ INVENTOR. GEORGE EL L/or J Km ATTQRNEV Patented Feb. 23, 1954 UNITED STATES ATENT OFFICE TELECOMMUNICATION SYSTEM' George Elliott,v Rochester, N.. Y., assigner to Stromberg-Carlson Company, a. corporation of New York Application December 26, 1951, Serial No. 263,375

(Cl. P19-18) 5 Claims.

rr11-is. invention relates to telecommunication systems and particularly to signaling arrangements in machine switching telephone systems.

The object or the invention is to promote. econonly and the speed and reliability of the operation of the switching facilities, particularly those placed in an oflce. such as a private dial oiiice normally unattended by maintenance. personnel.

The invention is embodied in the circuit arrangements of a step by step switch known as a selector-connector, that: is a switch used both for extending connections to single'lines through` directed movements in each 'of two directions andi to an. idle'one of a plurality of other lines through a directed. movement in a rst direction and an automatic movement in a second direction.

By the use of such aselector-connector a compact and reliable private dial ofce may be provided with means whereby the subscribers thereto may operate this switch to extend local con- 1 nections therethrough to other local subscribers stations or to lines leading to a central office. An

attendants cabinet is provided whereby calls incoming from the central oiiice may be answered and extended to any one of theY local subscribers and whereby general supervision over the system may be exercised.

A feature o the invention is a restricted service provision whereby access to any outgoing central oiice trunk may be denied to a particular local substation. This restrictedA service. provision is of a ilegible nature in that the service over only" a particular group of outgoing central olce trunks he denied andservice over others allowed. Thu-s, if' there are central ofhceoutgoing trunks on tivo or more levels the service from a particular substation may be denied over one or the other orali of the said levels;

A feature of the invention thus resides in a double marking means whereby service over an outgoing trunk may be restricted in'response to a marking or" the particular line andthe marking of a particular group of outgoing lines. If suchy marking absent in either case the connection may be established. Thus a line marked for restricted service may be prevented from establishing outgoing calls only over trunks also markedv as 'inaccessible to such restricted servicelines. A restricted service line may :freelyl make calls over outgoing trunks not so marked and al1 other sub.- statien not marked for restricted service may freely make calls over outgoing trunks marked for restricted service. y

A'feature oi the invention is-thus a 'selective arrangement 'for restricted service whereby subscribers stations marked forl restricted service may be selectively denied service over the trunks of a plurality of groups oi outgoing trunks.

In accordance with the present invention the switch has a plurality of means whereby anyone or more levels thereof may be marked for particular purposes. Thus one marking may be used to indicate that the outgoing lines of a level lead' to a central ofce and that the switch on that levelshould act as a selector while on otherlevels not so marked it-should operate asa connector.

Stated otherwise, there is a means for marking a level in a first manner to diierentiate the manner of the selection of the lines in that level from the manner of selection of the lines in levels not marking.

A feature of the invention is thus a plurality of marking arrangements for marking different levels of aswitch either singly or in combination. Thus, the switch after being directed to a given level may thereafter be operated either as a selector or a connector. Again within given levels containing either lines of one or another nature such as trunk lines to a central oliice or single and individual subscribers lines may be rendered inaccessible to other'subscriber lines individually` marked for restricted service. The present invention provides means whereby access to the lines of the executives of a company may be denied to lines serving certain of the maintenance and service personnel.

Another feature of the invention is the double use of certain relays under varying conditions. Specifically a relay conventionally known as a busy test relay and whose function has been to test for and detect the busy or idle condition of a line is now additionally caused to function as an interruptor relay, a function heretofore assigned to another and separate relay. The

busy test relay in the present arrangement not only acts as a test mean-s to prevent the actual connection to a busy line but now also acts to keep the switch moving in its automatic search for an idle one out of a plurality of equivalent lines. By the use of' the present arrangement a conventional relay may be entirely eliminated together with the wiring and the contact arrangements provided on other relays therefor.

A feature of the invention may therefore be stated as the provision in a switching device serving two or more classes of outgoing connections of a test relay responding in one manner to the busy or idle condition of the lines of one class and in another manner to the busy or idle condition of the lines of another class, performing a simple test function in the iirst instance and a double or test and operating function in another case.

Another feature of the invention is another double use of a conventional relay. Heretofore a so-called ringing trip relay has been used in each connector circuit for the purpose of detecting the answer of the called party and for thereupon disconnecting the ringing current and otherwise placing the circuit in condition for conversation. in the present case when av call is established over an outgoing trunk to the central oice it is not necessary to transmit ringing current and therefore the services of the ringing trip relay are not required. However, this relay will immediately respond to the trunk level marking, the condition which differentiates the level as one leading to trunks rather than as one leading to subscriber lines, and will thereupon convert the switch from a connector to a selector. The ringing trip relay, now, instead of standing by to operate upon` the answer of the called subscriber in the conventional manner will immediately operate and lock and in its operated condition will prepare for operation a different one of the cut through relays whereby a purely metallic circuit through the switch will be established when an idle trunk has been seized. One of the functions of this relay in the present arrangement is to control the ground to the common supervisory circuit including the enabling of the generator and certain tone sources.

A feature of the invention may therefore be stated as the provision of a relay for performing divers functions under divers modes of operation of the switch, performing a conventional operation when the switch is operating as a connector and another and unrelated operation when the switch is operating as a selector.

Other features will appear hereinafter.

The drawings consist of three sheets having five figures as follows:

Fig. 1 is a schematic diagram showing the organization of a private dial office having selector-connectors for extending the lines of the subscribers therein, both the subscribers lines and the trunk lines leading to central offices and an attendants cabinet for answering incoming calls and otherwise serving the system;

Fig. 2 is a block diagram showing how the three sheets of drawings may be placed to form a complete circuit diagram of the selecting arrangement of the present invention;

Fig. 3 is a schematic showing of a subscribers substation, the line circuit serving this subscribers line, a nnder switch and the allotter circuit therefor; and

Figs. 4 and 5 together give a complete circuit diagram of the selector-connector switch of the present invention.

In Fig. 1 there are indicated a plurality of line circuits l to l inclusive, the first of which is shown connected to a subscribers station 8, it being understood that the others are 4also so 4 connected. The line circuits 2, 5 and I are indicated as having a ground connection made thereto which will appear hereinafter to be a means for marking the particular lines served by these line circuits for restricted service. Each of the lines may be picked up and served by a finder switch 9, a common lead il) being indicated as extending through the line circuits to an allotter li for selecting for use and for putting into operation a nder such as the iinder 9. Each of these lines is also shown as emerging from a selector-connector l2 coupled to the iinder 9, thus when a substation such as 8 makes a call the starter wire I0 entering the allotter Il will cause the iinder il to pick up the incoming calling line and connect the selector-connector l2 thereto. The subscriber A at substation 8 may thereafter dial either two digits to select another one of these local subscribers lines or may dial a single digit to select a trunk line to a central office. In the drawing two such trunk lines I3 and Hl are shown each passing' through a two-way trunk line circuit i5 and IS' respectively and extending therefrom to a central oflice il and i8 respectively. These two trunk lines may be in the same switch level or for purposes of the present invention may rep" resent the trunk lines of two different levels.

An attendants cabinet i9 is provided for the purpose of answering incoming calls from the central office and for extending such calls to the lines lof the subscribers in this private dial office or otherwise to attend to the business of the eX- ohange. Lastly, a special trunk 2t accessible to the selector-connector is shown and marked as an information trunk to the operator.

Detailed description direction and these Wipers move over a bank of terminals corresponding to the various levels of the switch.

Within the switch circuit the battery connections `are shown as a minus and a plus, each within a small circle or enclosed'in parentheses. It is understood that the plus terminal of the battery is grounded so that hereinafter when a circuit is traced from battery to ground it will be understood that it is traced from the minus terminal to the plus terminal thereof.

In Fig. 3 a substation 2l is shown connected by dotted lines over its line to its line circuit. This line circuit consists essentially of a line relay 22 and a cut oif relay 23 so that when the subscriber at station 2l makes a call the line relay 22 will be energized. This relay, through its armature 2 and front contact, will ground the starter wire 24 leading to the allotter 25 which will enable the finder 26 so that the calling line is picked up thereby. In a conventional manner the calling line will be found and the selectorconnector associated with the nder 26 and, as shown in Figs. 4 and 5, will be seized. Upon the seizure of this selector-connector a ground -Will `be returned over the sleeve lead through the 5. front-contact andarmature I1 of the linetrelay 2'2 tot operate the cut oif relay 23 whichthereupon locks into the ground on the sleeve and cuts off the line relay from the Calling subscribers line. Within the line circuit in Fig. 3 a terminal 2.1 is shown-Withan indication below ofi a ground connection. This. ground connection may be made to the terminal 21 so that this particular line will be marked for restricted service. if the terminal 21 is not grounded within the line circuit of Fig. 3, then the subscriber on that line will have free access to ali lines served by the selector-connector ofFigs. 4 and' 5. The vterminal 21 constitutes a means whereby the individual line may be marked for restricted service.v

Seizure of selector-connector.

When this circuit is seized the loop over the tip and ring leads is closed through to the CB (call-` ing bridge) relay 28. The circuit may be traced from battery through the lower winding of the CB relay 28, the'normal contacts of armature 5 of the AB relay 29, the back contact and armature 4 of the SWT relay 30, ring of the line and thence over the circuit through the i'lnder to the calling substation 2| back over the tip of the line, armature 3 and back Contact of the SWT relay 3G, normal contacts of armature 4 of the AB relay 29, the upper winding of the CB 4relay 28, springs 6 and 1 of the X off normal contact set to a ground in the shelf supervisory circuit, here indicated as the lead GDT (ground-dial tone). If a dial tone is not required then a common ground connection may be made in the shelf supervisory circuit in place of the grounded dial tone connection indicated.

The CB relay responds to this circuit and through its armature I and front contact extends 'a ground through the armature 2 and backcontact of the Z (release) magnet 3l tothewinding of the RD (release delay) slow release relay 32 and thence to battery. The RD relay responds and through its armature and front contact places a ground on the master ground wire 33 for the purposes which will appear hereinafter. Through its armature 2 and front contact the RD relay grounds the sleeve wire leading back through the finder to the line circuit whereby the cut oif relay therein is operated. Through its armature 6 and front Contact the RD relay extends a ground to the lower winding of the SW (switch through) slow operating relay 34 to prepare this relay for operation. Ground placed on the master ground lead 33 is extended over contacts I and' 2 of the X off normal set to the upper winding of the XD (X delay) slow releasing relay 35 whereby this relay is operated. Likewise the ground on the master ground lead 33 is extended over contacts l and 2 of the Y oi normal set to the upper winding of the YD (Y delay) slow releasing relay 5K5, whereby this relay becomes operated. The three delay relays, the RD relay, the XD relay 35 and the YD relay 36 are thereupon operated for the purpose of controlling the switch in its response to the dial pulses from the calling substation 2 l.

Dialing first digit.

the loop is opened. During each of thesepulses the.: C B relay therefore restores and opens: the circuit forftheRDrelay. for-a short.- intervaldur- 6L. ing which, howeverthis relay dueto-its siowfreleasing;l characteristics, does not respond; The ground supplied for the operation of the-RD relayv is therefore switched over armature I. and back contact of the CB relay 28, armature 4 and front contact of the RD relay 32, back contact and armatureY 3 of the RT relay 31; armature 3 and front contact of the XD relay 35 and thence over a circuit having two branches, one of; whichextends through the lower winding of the XD relay. 35 to battery and the other of which extends through the winding of the X magnet 38 to battery. The X magnet 38 causes the T, R; S; HS, X and XX wipers 39 to 44 inclusive toistep forward in the primary direction of the switch. Upon the rststep of the switch the X off normal springs are operated in the direction indicated by the arrow so that the circuit for the XD relay through its upper winding is opened but this relay ismaintained in. operation through its lower winding during the pulsing; The X magnet has no slow release characteristics and hence responds separately to each impulse, but the XD relay has slow releasing characteristics and, therefore,V is maintained steadily operated until the complete train of pulses has been transmitted. At the end of this series of pulses the circuit for theX magnet 38 and the XD relay 35 isopened at the armature 3 of the XD relay 35 and at this point the circuit for the YD relay and the Y magnet is prepared.

Dialing second digit When thev subscriberdials the second digitthe circuit functions in the same mannerl as hereinbefore described with the exception that theground controlled by armature l of the CB relay' net and-the YD relay respond to thissecondtrain Lwipers 33 to 4I respectively move in the secondaryv direction of the switch, but the secondary and SS wipers dS-and 44 respectively remain in the positionl to which they were driven during the movement of the switch. When the switch takestherst step in the secondary direction the sec ondary off normal set of contacts operatesl in the direction indicated bythe arrow whereby the upu per winding of the YD relay itis opened that this relay for its continued operation depends upon the pulsing circuit thrmigh its lower winding. At' the end of this train of impulses the YD relay releases and the circuit of the Y magnet is opened. The'T, R, S and HS wipers of the switch have new been placed the terminals of the line identified by the two digits which. have beeny dialed. As soon4 as the terminals ofthe called iinehave been reached, and before theYD relay could release, a circuit was established from battery, the armature i and back contact ci the Z magnet 3l, armature 5:5 and back Contact of' the'BT relay it through the upper winding there` oi theV middle noninductive winding thereof in paralisi tobaclr contact and `arn'iature of the Y magnet it, sp1-ings t and' 5 of the overowcomtact set.. armature 5 and back. contact ofthe SW' relay 34, operated contacts of armature 6 of the YD-relay 3B, back contact and armature 5 of the SWT relay 30 to the S wiper 4I of the switch, whereby a busy test of the called line may be made. It will be noted shortly here that if the called line is busy then the S wiper 4l will extend this circuit to a ground for the operation oi the BT relay 45, whereas if the called line is idle this ground will not be found and the BT relay 46 will fail to operate.

Busy Zine If the called line had been busy then the BT relay will have operated in the manner just described. Upon operation this relay will be included in a circuit from battery, armature I and back contact of the Z magnet ill, the lower noninductive winding of the BT relay 45 and thence in parallel through the upper winding and the middle non-inductive winding thereof, back contact and armature of the Y magnet 15, springs 4 and 5 of the overiiow set, armature 5 and back contact of the SW relay 34 through the back contact and armature S of the YD relay 35, as soon as this relay releases, the front contact and armature 4 of the BT relay 46, the front contact and armature 6 of the RD relay 32 to ground, whereby this busy test relay will remain locked in its operated position. The operation or the BT relay thus closes a locking circuit for itself, when the YD relay restores, to a firm ground supplied by the RD relay 32.. Busy tone from the BT lead in the shelf supervisory circuit is now extended over the back Contact and armature 3 of the YD relay 36, the armature 2 and front contact of the BT relay 45, back contact and armature 3 of the SW relay 34, upper winding of the AB relay 25 through the talking bridge condenser 4l', the normal contacts of armature 4 or' the AB relay 29, the back contact and armature 3 of the SWT re lay 39 to the tip side of the calling line, whereby busy tone is transmitted to the calling subscriber.

Switch through sleeve wiper 4l the armature 'd and back contacty of the SWT relay 30, back contact and armature of the YD relay 36, lower Winding of the SW relay 34, back contact and armature of the BT relay 4B, front contact and armature 6 of the RD relay 32 to ground. The SW relay responds and locks through its upper winding, its front contact and armature 2 to the master ground wire 33.

At its armature l and back Contact the SW relay' opens the circuit between the RA lead in the shelf supervisory circuit and the winding of the Z release magnet Si. At its armature 4 and front contact the SW relay 34 extends a connection from the generator lead in the shelf supervisory circuit through the front contact and armature 4 of the SW relay 34, the lower winding of the RT relay 3i', the back contact and armature 1 of the RT relay 37, armature 3 and front contactl l of the SW relay 34 to the ring wiper 4i! of the switch, thence over the network of the called substation including the ringer thereof, the tip wiper contact of the RT relay-31 to ground so that the ringer of the called substation is operated.I Through its armature Q and front contact the SW relay 34 places a iirm ground on the sleeve wiper 4iof the switch to mark the seized equipment as busy. Through its armature lll and front contact the SW relay connects the HS wiper 42 of the switch into a connection established by the CB relay 28 and used for purposes with which we are not at present concerned.

Ringing Ringing current is supplied over the circuit hereinabove described. The RT relay 3l does not operate at this time. Ring back tone is supplied from the armature 8 of the SW relay 34, over which the ringing current is being supplied through the condenser 4t, the condenser 49, the back contact of armature 5 of the AB relay 29, the baci: contact and armature 4 of the SWT relay 3l) to the ring side of thecalling subscribers line, whereby this calling subscriber is given an indication that ringing current is being applied to the called line.

Called party answers It is conventional to superimpose the ringing current on a direct current source, or otherwise to supply tripping battery, and hence it will be assumed that the current nowing from the generator lead in the shelf supervisory circuit includes a direct current component which now supplies enough current through the circuit oi the called substation when the called subscriber thereat has answered to operate the RT relay 3l. This relay may be of a conventional two step design having at least one very sensitive armature so that responsive to the answer of the called subscriber the preliminary X contacts thereof, here shown as armature 4 and front contact of the RT relay 31, will operate. This will close a local cil cuit from the master ground wire 33 to the upper winding of the RT relay 3l", whereby the other armatures thereof are operated. Operation of the RT relay 3l through the movement of its armature I removes ground from the start wire leading into the common supervisory circuit. Through its armatures 6 and 'l the RT relay disconnects the ringing source from the called line and by the same token disconnects the ringing tone transmitted to the calling line. The circuit is thereupon switched through from the calling to the called line in what may be termed a battery4 feed connection. That is, the circuit between the calling and called line is separated by the transmission condensers 41 and 49, but talking battery is supplied to the calling line by the windings of the CB relay 28 and talking battery is supplied to the called line through the windings of the AB relay 29. armature 3 of the SW relay 34 is connected through the upper winding to the tip side of the-i called line connection. Battery is extended through the lower winding of the AB relay 2S,

thence through the iront contact and armature S of the SW relay 34 to the ring side of the called line connection. The AB relay responds to the bridge supplied by the called substation circuit. Through its armatures 4 and 5 the AB relay reverses the current now to the calling substation for conventional purposes. Through its armature 3 and front contact the AB relay 29 supplies an alternate ground from the W wiring to the master ground wire 33.

Ground through the front contact and- As indicated, the.' W wiring may or may not be employed. The

9 results 'of its employment will Abe noted hereinafter.

The conversation may now take place.

Release If the lf wiring is used then the circuit will be converted to one known as last party 1re lease, that is the circuit Willbe held yuntil both parties release.

Calling party disconnects first When the Acalling party disconnects the loop over the tip and ring leads tothe CB relay 'rid opened and .the circuitrestores and vin turn lopens the circuit for theRD relay 'The El) relay restores and preparesa partial path from the En lead in the shelfsupervisory circuitover armature i and back contact for the 'operation of the Z magnet, as will be described hereinafter. The RD relay removes the ground from the master ground wire 33, but .tli'm is held ,through the iront contact and armature 3 of the AB relay when the W Wiring is used. A ground is now extended from armature f5 and back-contact oi the RD relay li2 .through the front contact andarmature v2 of the AB relay '2Q to the upper windingof the XD relay 25. During the rel-ease time lof the RD re lay-'and the operatetimelof the XD relay there is an absence of rground `on'the sleeve ywire'leading back to the 'calling substation allowingthe preceding equipment rto release. However, as soon as the XD -relayfopera-tes another ground is extended from armature vI and front contact of 'the AB -relay 29 to armature l and front contact of the '-XD relay 35 'to the-sleeve-extending b ck to the'calling subscriber to mark this-switch as busy and therefore unavailable for use at present. TheRT relay 3'1 and theSW relay {ill-remain operated from the ground'on the master wire When the called party disconnects-the loop over the tip and ringleads to the AB vrelay 23 isopened and this relay releasing vremoves the groundsupplied r`by the W Wiring to the master grou-nd wire 33 and thus releases the RT and SW 'relays and'removes the ground from the sleeve lead extending bacl: toward the calling subscriber. The SW -relay in lrestoring removes ground irom the sleeve wiper of the Vswitch leading to the called terminal, opens the talking path andthe transmission circuit to the AB relayand closes a circuit from the -RA lead to the Z release magnet '31. A low resistance ground on the RA lead '(not shown) is extended through-armature i andbaclr. con-tact of the SW relay v3ll, armature i and'bacl: Contact of the RD relay 32, armature l and l'back contact of the SWT relay 'through springs d and 3 of the X orf normal set and in ,parallel therewith, the springs aand-3 of the Yori normal set, the winding of the Z magnet 3i to battery, whereby the Z magnet is operated to release the wipers of the switch and return them to their normal positions. Through its `armature A2 and front contact the'Z magnet places ground on vthe sleeve leading toward the calling subscriber to maintain -abusy indication vfor'this switch until it is completely released. When the switch 'vreturns to 'normaltheX o'ifnormal and Y oir" rnormal springs restoreand open vthecircuitof Lthe Z release magnet. The Z m-agnetrestoresallowing the `springs thereof to move back in the 'normal position and removeground from the sleevelea'ding toward the calling :line so that this "switch now is completely released and available for further service.

Called party disconnects first When the called party ldisconnects rst the loop over the tip andring leads to the AB :relay 2d is opened. The AB relay di) restores and removes the ,alterna-ite ground connection to the `master ground wire et supplied l the W wiring if used. The AB .relay .alsoreverses battery over the tip ringleads to the cailingline. When the calling party disconnects the `loop over .the tip :and ring leads `to lthe CB relay 2 8 is opened, the relay restores and opens the ,circuit ior'the RD relay The RD relay restores, prepares 4.path ol' a circuit to the RAleadfor operationor' the l release magnet, opens the master ground circuit andremoves groundirom the back sleeve, vallowing the preceding switches to release. The XD relay 3.5 does not operate attln's time vdue to the fact that the .AB relay has opened the circuit heretofore described. .The RT relay, depending on the masterground over wire 3.3., restores and likewise the SW relay restores, thus placing the switch in condition for ,complete release which takes place as .above described.

If .the "W wiring is not used, the .circuit will release when thecalling party hangs up.

Switch through on marked level When this circuit is seized 4by the preceding equipment the circuit functions as described hereinbeiore. When the XD :relay restores after thedialing ofthe desired rst ,digita marking ground willcause the operation of the LRT and 13T-relays. The ground is indicatedin the l right hand portion .of Fig.5 marked M Wiring.

Wherever a particular level of the switch is -to be used for extending connections to trunk lines leading to a central oce or where, for any other purpose, the switch is to be converted to selector operation, then the corresponding terminal of the bank of terminals traversed by the X wiper dwill be grounded as indicated. Assumingthat a marked rlevel has been reached, .then this ground will ybe extendedfover the X wiper 43, armature 2 and back contact ofthe XD relay 3.5 lupon the release of this relay, armature :I and `front contact of the YD relay 3.5, .armature and back contactof the RT relay Gland/thence through the ,upper vwinding of the relay to battery. The RT relay first operatesitsvarmature 4 and front contact to lock this relay into the master ground Wire 33 and thereafter -operates the rest of its contacts. Operation of the ,RT relay 3l at its armature I and backcontact removes ground from the start lead and closes a circuit 4for the SWT relay 30 which will become effectiveas hereinafter described. The ABT relay will start to operate from the marking ground over the X wiper 43, the armature `2 and back contact `of the XD relay 35, the armature l-and front-contact of the YD relay 36, the back contact and armature 2 of the -RT relay 3l,the springs 'land e ofthe Y off normal set, the armature and back `contactof the Y magnet riii to the winding of the BT relay 4B vand thence througna circuit hereinbefore described. However, `the armature dbf the -R'Irelay 37 is fast operating and will'extend the` master ground ,-33 to the BT relay d6 to insure the loperationfof this latter relay even after the original circuit above described has been opened at the back contact of armature 2.0i the RTrelay 31. The BT relay operates in this circuit and closes a circuit frorthe YD relay 35 and the Y magnet in parallel. This circuit 'may be traced from ground, armature "S and" front vcontact Aof the RD relay 32, armature 4 and front contact of the BT relay 46, armature 4 and front contact of the YD relay 35, iront contact and armature 3 of the RT relay 31, armature 3 and back contact of the XD relay 35, armature 2 and front Contact of the YD relay 36 to the point where the circuit divides, going in one direction through the lower winding of the YD relay 36 and in the other direction through the winding of the magnet 45. The YD relay is heid operated through its lower winding and through virtue of its slow releasing characteristic during the following automatic operation. The Y magnet operates over the above path stepping the switch one step in the Y direction and by means of the Y oir` normal contacts opens the original operating circuit of the YD relay 36 and the original operating circuit of the BT relay 46. The BT relay restores and, in turn, opens the operating circuit of the YD relay and the Y magnet, but the YD relay remains operated during pulsing because of its slow releasing characteristics. The Y magnet restores and connects the BT relay to the forward sleeve wiper 4i. If the first line is busy, ground on the sleeve bank is forwarded over the associated wiper through armature 5 and back contact of the SWT relay 30, operated contacts of armature 6 of the YD relay 35, armature 5 and front contact of the RT relay 31 to maintain a ground on the right hand terminal of the SWT relay 30 to maintain this relay short circuited and to prevent its operation until an idle line has been encountered. The

BT relay 46 reoperates and recloses the circuit for the operation of the YD relay 35 and the Y magnet 45. The circuit continues to function as above described and the alternate operation of the BT relay 46 and the Y magnet 45 continues until an idle line is found or until the switch steps to the overflow position, where the overflow contacts shown in the upper left hand portion of Fig. 4 are operated. Absence of ground on the sleeve bank indicating an idle line will prevent the BT relay 46 from operating, thus extending Abattery through normal contacts of the Z magnet 3|, the BT relay in its unoperated position, the back contact and armature of the Y magnet 45, the contacts 4 and 5 of the overflow set of contacts, armature 5 and back contact of the SW relay 34, armature 5 and front contact of the RT relay 31, the winding of the SWT relay 33 to ground on the sleeve lead leading to the calling substation. The SWT relay 36 and the BT relay 46 are thus placed in series, but the BT relay, being of comparatively much lower resistance than the SWT relay, will not be able to derive sufficient current for its operation;`

hence the SWT relay 3B will operate whereas the BT relay 45 in series therewith will remainl unoperated. The SWT relay 39 operates and closes the tip and ring leads of the preceding equipment through to the tip and ring wipers 39 and 45 in a clear metallic circuit. The circuit of the CB relay 28 is opened and this relay` releases. The SWT relay through its armature 2 and front contact provides a circuit for itself in series with the BT relay independent of the circuit through armature 5 and front contact of the RT relay 31. Through its armature 5 and' front contact the SWT relay extends ground on the sleeve lead of preceding equipment through to the brush of the forward sleeve wiper 4i.

under control of ground extended from the sleeve lead in following equipment, such as the .twoway trunk l5' or I6, and opens the master ground wire 33, thus releasing the RT relay 31. The RT relay restores and opens the original battery circuit to the SWT relay 35 thus placing the SWT relay under control of its own iront contact and armature 2. When the calling party releases, ground is removed from the controlling equipment which will cause the SWT relay 30 to release. The SWTlrelay restores and closes a circuit from the RA lead in the shelf supervisory circuit to the Z release magnet, as hereinbefore described. A low resistance ground on the RA lead forwarded through normal contacts of the SW relay 34, the RD relay 32 and the SWT relay 3U through the operated X off normal and Y oir normal contacts is extended to the Z magnet as hereinbefore described to cause the magnet to operate and release the switch to its normal position.

Restricted service wiring The restricted service wiring is noted as the N wiring and consists in a connection from the HS incoming wire of the switch to any one or more of the contacts traversed by the XX wiper 44. After the XD relay 35 restores at the end of the first train of dial pulses, if this N wiring is used and the XX wiper 44 is resting on a terminal thus marked, a circuit will be established from ground in the line circuit Fig. 3 providing the terminal 21 of that line circuit is grounded, over the HS lead, the marked terminal of the XX wiper 44, thence over` the strap 55 used when the N wiring is used, armature 4 and back contact of the XD relay 35, back contact and armature 5 of the SWT relay 39 to the forward sleeve wiper 4I, thus placing an articial busy indication on this sleeve wiper whereby no idle trunk or line may be detected. The ground armature 4 of the XD relay 35 will also be extended over the front contacts of armature S of the YD relay 35, the back contact and armature 5 of the SW relay 34, springs 5 and 4 of the overiiow set, springs 6 and 1 of the Y oli normal set to the winding of the RT relay 31 which thereupon operates so that the switch will again be caused to operate automatically to the overiiow position so that service will be denied to the calling subscriber thus marked for restricted service.

Thus it will be noted that after the end of the irst train of pulses when the XX wiper 44 cornesv to rest on any terminal marked for restricted service, the switch will be stepped automatically t0 its overow position regardless of any mark! ing or absence of marking for the correspond-- ing X wiper 43. If the X wiper 43 encounters a marked terminal but the XX wiper does not encounter a correspondingly marked terminal, then the switch will automatically step to the rst idle line. Hence it will be clear that a restricted line may be given access to eitherY individual lines or to trunks in levels where the XX wiper 44 does not encounter a marked terminal and may be denied service to either individual lines or to trunks in all levels where the XX wiper encounters marked terminals. I By Way of example, if a restricted subscribers line drives the switch to either the level 6 or 3, the switch will automatically move to the overflow position, but if moved to the 8 level will auto-' matically move to seek an idle trunk. -If a nonrestricted line drives the switch t0. either level.

eminence 113 9 for 0 the automatic movement 4asiarselectni' will take place, but on any-other Vlevelthevsvvitch-vvll actas alconnector.

Busy tone on overflow armature 3 of the SW relay 34, through the upper y winding of the AB relay 2-9, through the -bridge condenser 41 to the calling line to .notify the subscriber thereat that he has encountered a busy line, or, in other words, that no connection can 'be made to this called line.

'What is .claimed is:

l. In a telecommunication system, a plurality of subscriber lines each including a station and a line circuit, a selector-connector for extending said lines to selected terminals of any one of a plurality of outgoing lines, the plurality of terminals of said outgoing lines being grouped, first means for marking selected ones of said groups of outgoing line terminals in one manner to identify said groups as connecting to outgoing trunk lines, second means for additionally marking selected ones of said rst ,marked groups to identify the additionally marked groups of outgoing terminals as connecting to outgoing lines designated to be restricted from connection with a certain class of subscriber line, a relay in the circuit of said selector-connector responsive to a given operation of a selected line connected to one of said unmarked group terminals, said relay being operated in response to said first marking means, and means responsive to the operation of said relay by said first marking means for converting the circuit of said selector-connector from one suitable for extending a connection from one of said subscriber lines to any desired line connected to outgoing terminals in an unmarked group of outgoing line terminals to one suitable for extending a connection to outgoing terminals of any lines ina group of outgoing terminals marked by said rst marking means only.

2. In a telecommunication system, a plurality of subscriber lines each including a station and a line circuit, a selector-connector for extending said lines to selected terminals of any one of a plurality of outgoing lines, the plurality of terminals of said outgoing lines being grouped, means for marking selected ones of said groups of outgoing line terminals in a manner to identify said groups as connecting to outgoing trunk lines, a circuit arrangement for said selectorconnector including a relay responsive to a given operation of a selected line connected to one of said unmarked group terminals, said relay being also operated in response to said marking means, means in said circuit arrangement for establishing a divided battery feed talking path through said selector-connector, means for establishing a clear metallic path through said selector-connector, and means responsive to the operation of said relay by said marking means for controlling the operation of said last-named means to establish the clear metallic path through the selectorconnector.

3. In a telecommunication system, a plurality of subscriber lines each including a station and a line circuit, means for marking any one or more of said lines for restricted service, a selector- 14 connector switch for .extending said linzes, aa cire cuit arrangement'for said switch including means to .operate said switch es a connector `and to lconvert the said circuit to operate said switch as a selector, said lswitch .having terminals xarranged .in groups, means for `marking said groups for'selector operation and other means for .marking ysaid 4groups 'for restricted service, .Isa-id switch circuit 'including a relay :for testing .for the idle or .busy @condition of ya selected line, said .relay being :responsive .to :said first group marking means for additionally controlling :said selector operation, va second relay for detecting the answer of 1a subscriber "on a called line connected 5to a terminal .in one 4of :said unmarked groups, said second relay being responsive to 'said first `group marking means .for .conuertin'gzsaid switch .circuit from connector to .selector operation, and means jointly responsive to saiel second group marking means fand said subscriber line 'marking means "to place :an `artificial busy condition on saidfswitch circuit to prevent the detection of said nrst relay of an idle selected line.

4. In a telecommunication system, a plurality of subscriber stations, a line circuit for eachof said subscriber stations, means for marking any one or more of said line circuits for restricted service, a selective switch, said switch having groups of outgoing line terminals, means for connecting any one of said line circuits to said switch, said switch having a set of brushes movable in a first direction to select a group of outgoing line terminals and in a second direction to select terminals of individual outgoing lines. said switch having an auxiliary brush for movement in a rst direction only as said set of brushes is moved in the first direction, a set of auxiliary brush terminals for said auxiliary brush positioned for each auxiliary terminal to be individually and successively contacted by said auxiliary brush as said switch is moved in the rst direction to positions with said set of brushes contacting individual and successive groups of line terminals, means for marking selected ones of said auxiliary brush terminals, and means connecting said auxiliary brush to the marking means for any one of the marked line circuits to establish a circuit from a marked one of said subscriber station lines over a said marked auxiliary brush terminal for preventing the establishment of a connection from a marked line circuit to any outgoing line in the group of outgoing line terminals selected by a iirst movement of the switch to a position with the auxiliary brush in contact with a said marked auxiliary brush terminal.

5. In a telecommunication system, a plurality of subscriber stations, a line -circuit for each of said subscriber stations, means for marking any one or more of said line circuits for restricted service, a selective switch, said switch having groups of outgoing line terminals, means for connecting any one of said line circuits to said switch, said switch having a set of brushes movable in a first direction to select a group of outgoing line terminals and in a second direction to select terminals of individual outgoing lines, said switch having a rst auxiliary brush for movement in a first direction only as said set of brushes is moved in the first direction, a set of rst auxiliary brush terminals for said first auxiliary brush positioned for each auxiliary terminal to be individually and successively contacted by said flrst auxiliary brush as said switch is moved in the rst direction to positions with said set of brushes contacting individual and successive groups of line terminals, said switch having a second auxiliary brush for movement in a first direction only simultaneously with the movement of said rst auxiliary brush, a set of second auxiliary brush terminals for said second auxiliary brush positioned for each auxiliary terminal to be individually and successively contacted by said second auxiliary brush as said switch is moved in the rst direction to positions with said set of brushes contacting individual and successive groups of line terminals, means for marking selected ones of said rst auxiliary brush terminals, means connecting said rst auxiliary brush to the marking means for any one of the marked line circuits to establish a circuit from a marked one of said subscriber station lines over a said marked first auxiliary brush terminal for preventing the establishment of a connection from a. marked line circuit to any outgoing line in the group of outgoing line terminals selected by a first movement of the switch to a position with i6 the rst' auxiliary brush in contact Witha said marked first auxiliary brush terminal, means for marking selected ones of said second auxiliary brush terminals, and means connecting said second auxiliary brush to said selective switch to cause said switch to operate automatically in the second direction When said second auxiliary brush is contacting a marked second auxiliary brush terminal upon completion of the movement of the switch in the first direction.

GrEORGrEr ELLIOTT.

References Cited in the file of this patent 'UNTED STATES PATENTS Number Name Date 1,424,644 Herink Aug. 1, 1922 1,468,078 Ray et al Sept. 18, 1923 1,492,995 Lubberger May 6, 1924 2,005,595 Roome et al June 18, 1935 2,258,651 Hovland Oct. 14, 1941 

